House-dust-mite induced features of asthma in marmoset monkeys
Translational animal models for human asthma are necessary, especially for preclinical drug testing. The small-bodied New-World monkey species common marmoset (Callithrix jacchus) is particularly suitable to develop an animal model that is close to humans but more reasonable and easier to handle than classic primate models in macaques. The hypothesis was that it is possible to sensitize marmosets against house-dust-mite (HDM) to generate an asthma-like condition including lung eosinophilia and allergen-specific secretion of interleukin 13 (IL13) from peripheral blood mononuclear cells (PBMC). Twelve animals were sensitized against HDM extract (Greer) over a course of six weeks. Sham-sensitized animals (n=6) only received the adjuvant. A month after sensitization, intratracheal (i.t.) HDM allergen challenge was performed for half of these animals to date. PBMCs were isolated from blood before and after sensitization. 2x105 cells were seeded in cell culture medium and stimulated with 10<mju>g/ml HDM and 10<mju>g/ml HDM plus 50<mju>g/ml dexamethasone (ratiopharm), respectively. 96h after cultivation under cell culture conditions, supernatants were collected and evaluated. Detection of IL13 was performed using a commercial ELISA (UCyTech). Bronchoalveolar lavage (BAL) was performed before and after the challenge phase and BAL fluid (BALF) was analyzed for cytokines and cellular composition. Allergen stimulated PBMCs of sensitized marmosets showed higher IL13 levels post sensitization, compared to pre-sensitization and sham-sensitized animals (34.2±10.5, 2.5±0.7 and 6.8±4.1pg/ml; mean±SEM; p=0.001 Wilcoxon test and p=0.024 Mann-Whitney test; n=12/6). HDM-induced IL13-release could be drastically reduced by dexamethasone (1.3±0.2pg/ml; mean±SEM; p=0.016 Wilcoxon test; n=7). Total cell counts for sensitized animals increased after HDM-challenge (3.0±0.5x105 vs. 1.3±0.3x105 cells/ml BALF; mean±SEM; p=0.031 Wilcoxon test; n=6). Likewise eosinophil numbers in BALF rose for sensitized animals (14.0 vs. 0.8%; median; p=0.031 Wilcoxon test; n=6) but not for sham-sensitized animals (1.5 vs. 1.0%; median; n=3). IL13 levels measured from BALF supernatants were slightly higher for sensitized animals after HDM-challenge. Further investigations of cutaneous reactivity towards HDM revealed positive reactions for half of the sensitized animals. HDM-specific IL13 secretion of marmoset PBMCs indicates a successful sensitization against HDM. Allergen challenge of sensitized animals resulted in an influx of cells, predominantly eosinophils, into the lung, a characteristic feature of asthma in humans. Novel readout parameters such as detection of asthma-relevant cytokine levels via real-time PCR and measuring immunoglobulin levels are under investigation.